1. Field of the Invention
The present invention relates to a hydraulically damped mounting device. Such a device usually has a pair of chambers for hydraulic fluid, connected by a suitable passageway, and damping is achieved due to the flow of fluid through that passageway.
2. Description of the Related Art
EP-A-0115417 and GB-A-2282430 discussed a type of hydraulically damped mounting device for damping vibration between two parts of a piece of machinery, e.g. a car engine and a chassis, referred to as a “cup and boss” type of mounting device, in which a “boss”, forming one anchor part to which one of the pieces of machinery was connected, was itself connected via a deformable (normally resilient) wall to the mouth of a “cup”, which was attached to the other piece of machinery and formed another anchor part. The cup and the resilient wall then defined a working chamber for hydraulic fluid, which was connected to a compensation chamber by a passageway (usually elongate) which provided the damping orifice. The compensation chamber was separated from the working chamber by a rigid partition, and a flexible diaphragm was in direct contact with the liquid and, together with the partition formed a gas pocket.
In the hydraulically damped mounting devices disclosed in the specifications discussed above, there was a single passageway. It is also known, from other hydraulically damped mounting devices, to provide a plurality of independent passageways linking the chambers for hydraulic fluid.